Theoretical and experimental vibrational study of phenylurea: structure, solvent effect and inclusion process with the beta-cyclodextrin in the solid state.

FTIR and Raman vibrational spectroscopic techniques as well as DFT quantum chemical calculation were used for characterizing conformational changes of phenylurea (a herbicide parent molecule) occurring from solid state to aqueous medium. Experimental infrared frequencies were assigned on the base of urea and benzenic derivatives spectroscopic data available in the literature and vibrational normal modes analytical calculation at the fully optimized geometry. Investigation of isotopic and solvent effects has revealed that the structure of phenylurea is particularly sensitive to the electrostatic environment via hydrogen non covalent bonds. The ability of beta-cyclodextrin (beta-CD) to form host-guest inclusion complex with phenylurea in the solid state was also evidenced by significant frequency shifts observed in the 1400-1800 cm(-1) spectral range.